Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts formed of biocompatible materials (e.g., Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing) have been employed to replace or bypass damaged or occluded natural blood vessels. A graft material supported by framework is known as a stent-graft or endoluminal graft. In general, the use of stent-grafts for treatment or isolation of vascular aneurysms and vessel walls which have been thinned or thickened by disease (endoluminal repair or exclusion) are well known. Many stent-grafts, are “self-expanding”, i.e., inserted into the vascular system in a compressed or contracted state, and permitted to expand upon removal of a restraint. Self-expanding stent-grafts typically employ a wire or tube configured (e.g. bent or cut) to provide an outward radial force and employ a suitable elastic material such as stainless steel or Nitinol (nickel-titanium). Nitinol may additionally employ shape memory properties. The self-expanding stent-graft is typically configured in a tubular shape of a slightly greater diameter than the diameter of the blood vessel in which the stent-graft is intended to be used. In general, rather than graft placement in a traumatic and invasive manner such as open surgery, stents and stent-grafts are preferably deployed through a less invasive intraluminal delivery, i.e., cutting through the skin to access a lumen or vasculature or percutaneously via successive dilatation, at a convenient (and less traumatic) entry point, and routing the stent-graft through the lumen to the site where the prosthesis is to be deployed.
Intraluminal deployment is typically effected using a delivery catheter with coaxial inner (plunger) and outer (sheath) tubes arranged for relative axial movement. The stent graft is compressed and disposed within the distal end of an outer catheter tube in front of an inner tube. The catheter is then maneuvered, typically routed though a lumen (e.g., vessel), until the end of the catheter (and the stent-graft) is positioned in the vicinity of the intended treatment site. The inner tube is then held stationary while the outer tube of the delivery catheter is withdrawn. The inner tube prevents the stent-graft from being withdrawn with the outer tube. As the outer tube is withdrawn, the stent-graft radially expands from a proximal end to a distal end of the stent-graft so that at least a portion of it is in substantially conforming surface contact with a portion of the interior of the lumen e.g., blood vessel wall or anatomical conduit. The proximal end of the stent-graft is the end nearest to the heart by way of blood flow whereas the distal end is the end furthest away from the heart during deployment.
Most stent-graft deployment systems are configured to have the proximal end of the stent-graft deploying as the outer tube or sheath is pulled back. The proximal end of the stent-graft is typically designed to fixate and seal in the vessel during deployment. Unfortunately, this configuration leaves little room for error in placement since re-positioning the stent-graft after initial deployment is usually not possible. Deploying the proximal end of the stent-graft first makes accurate pre-deployment positioning of the stent-graft critical.
One attempt to overcome this problem by W. L. Gore utilized a flexible jacket that deploys the stent-graft with a ripcord that opens the jacket along the longitudinal axis of the flexible jacket, e.g., U.S. Pat. No. 6,315,792. Unfortunately, this method introduced a separate non-integrated sheath into the system into the femoral artery and further failed to provide the desired control during deployment. Other stent-graft delivery systems have also attempted to confine the proximal end of the stent-graft, but generally fail to provide adequate control in manipulating the stent-graft positioning in both the initial deployment of the stent graft and the re-deployment of the stent-graft (once the stent-graft has been partially deployed). Another problem encountered with existing systems, particularly with systems that have a distal end of a stent-graft fixed during deployment (or during the uncovering of a sheath) is the frictional forces that can cause the stent-graft to axially compress or bunch up. This bunching increases the density of the stent-graft within the sheath and further increases the frictional drag experienced during deployment.
Another indication requiring further control in the deployment of stent-grafts is the need for an effective method of deploying branch grafts. Patients diagnosed with aneurysms involving renal arteries or other branch arteries are typically excluded from endovascular grafting because most endovascular grafting systems are not designed for use in regions of the aorta from which side branches extend. Most if not all of the endovascular grafts which have been designed for use in treating infrarenal aneurysms, for example, require that a proximal “neck” (e.g., at least two (2) centimeters of non-aneurysmic aorta) exist inferior to the renal arteries, to provide a region where the superior end of the graft may be securely anchored in place, without blocking or restricting blood flow into the renal arteries. The deployment of endovascular grafts within regions of the aorta from which branch arteries extend (e.g., regions of the aorta from which the renal, superior mesenteric, celiac, intercostal, and/or subclavian arteries emanate) present additional technical challenges because, in those cases, the endovascular graft must be designed, implanted and maintained in a manner which does not impair the flow of blood into the branch arteries.
U.S. Pat. No. 5,425,765 (Tiefenbrun et al.) describes an endovascular graft which has one or more openings or fenestrations formed at specific locations, to allow blood to flow from the aorta into one or more branch arteries. However, such fenestrations do not form discrete conduit(s) through which blood is channeled into each branch artery. As a result, the area surrounding the fenestrations could be prone to i) the leakage of blood into the space between the outer surface of the aortic graft and the surrounding aortic wall or ii) post-implantation migration or movement of the graft causing misalignment of the fenestration(s) and the branch artery(ies)—with resultant impairment of flow into the branch artery(ies).
U.S. Pat. No. 5,984,955 (Wisselink) describes a system and method for endoluminal grafting of a main anatomical conduit (e.g., the aorta) and various branch conduits (e.g., side branch vessels such as the carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, or renal arteries-or furcations such as the iliac arteries) which emanate from the main anatomical conduit. The Wisselink grafting system generally comprises a primary graft having at least one opening therein for at least one branch graft which is passable through the opening of the primary graft and into the branch anatomical conduit(s) such that the proximal end of each branch graft is in substantially fluid-tight sealing contact with the primary graft. The embodiments discussed in Wisselink illustrate a protruding branch graft connector that protrudes from the main graft that includes a rigid or semi-rigid frustoconical member that extends outwardly. The protruding frustoconical member would likely add frictional forces during deployment of the main graft and would further impede efforts in any attempts to re-deploy the main graft in a different orientation or position once initially deployed and anchored. Additionally, the Wisselink system may experience difficulty tracking the branch graft through branch anatomical conduits without the use of a cap. The Wisselink system also discloses a main or primary graft that has first and second ends that fix or anchor to the main anatomical conduit during deployment of the branch grafts. In other words, the main graft in Wisselink is anchored before the complete deployment of both the main and branch grafts.
The accompanying figures include various showings of human anatomical structures, and such anatomical structures are labeled according to the following legend:                Aorta . . . A        Celiac Artery . . . CA        Femoral Artery . . . F        Heart . . . H        Iliac Arteries . . . IL (IL.sub.1 and IL.sub.2)        Kidneys . . . K        Renal Arteries . . . RA (RA.sub.1 and RA.sub.2)        Superior Mesenteric Artery . . . SMA        
As shown generally in FIGS. 1-1D, prior art endoluminal grafting system 10 generally comprises a primary graft 12 having at least one branch graft opening 14 formed therein, and at least one branch graft 16 which is advanceable out of the branch graft opening 14 and into a branch anatomical conduit (e.g., a side branch or furcation of a blood vessel). A branch graft connector apparatus 17 is incorporated into the primary graft 12 and/or branch graft(s) 16 to connect the proximal end of the branch graft(s) 16 to the primary graft 12. One or more primary graft anchoring devices 18, such as radially expandable stent(s) or frame(s), is/are used to frictionally hold the primary graft 12 in a fixed position in the lumen of the primary anatomical conduit (e.g., aorta). Also, where necessary, one or more branch graft anchoring devices 20, such as radially expandable stent(s) or frame(s), may be used to frictionally hold at least the distal end of the branch graft(s) 16 in fixed position in the lumen(s) of the branch anatomical conduit(s) (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, renal or iliac arteries). These primary graft anchoring device(s) 18 and branch graft anchoring device(s) 20 may be formed or incorporated into the body of the primary and branch grafts 12, 16 or, alternatively, they may be formed as separate structures (e.g., separate self-expanding or pressure-expandable stents) which are positioned within the lumens of the primary and branch grafts 12, 16, to accomplish the desired anchoring of the primary and branch grafts 12, 16, as shown.
Each branch graft opening 14 of the primary graft 12 is strategically placed, and preferably reinforced and marked for radiographic visualization, to facilitate precise alignment of each branch graft opening 14 with the particular branch anatomical conduit (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, renal or iliac arteries) into which its branch graft 16 is to extend. The desired strategic placement of each branch graft opening 14 may be facilitated by custom-forming the branch graft opening(s) 14 in the primary graft 12, prior to implantation of the primary graft 12. Such pre-implantation, custom formation of the branch graft opening(s) 14 may be accomplished through the use of spiral computed tomography data of the vascular anatomy of the particular patient in whom the endovascular grafting system 10 is to be implanted. Notably, in applications where the primary graft 12 is being prepared for implantation in the thoracic or thoracoabdominal aorta, the branch graft openings 14 may be sized and positioned to align with relatively small side branch vessels (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, or renal arteries) which, unlike the iliac bifurcation at the inferior end of the aorta, require a branch graft 16 be passable through such branch graft opening(s) 14 and into the smaller side branch vessel (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, or renal arteries) at an angle of approximately 80-90 degrees upwardly or downwardly relative to the axis of the aorta.
Once mapped a customized stent graft with branch graft opening(s) 14 having been formed at the mapped side branch locations (including branch graft connector(s) 17), the primary graft 12 is inserted via an introducer into the femoral artery, and advanced under radiographic guidance into the site (e.g., the aneurysm) where the primary graft 12 is to be deployed. This insertion of the primary graft 12 (and any primary graft anchoring device(s) 18 which are formed separately from the graft 12) may be facilitated by mounting the primary graft 12 (and any such separate graft anchoring devices 18) on a balloon catheter or other suitable delivery catheter capable of carrying the primary graft (and any separate graft anchoring device(s) 18) to the intended site of deployment. The primary graft 12 and any separate primary graft anchoring device 18 is/are then radially expanded or otherwise deployed such that the primary graft becomes anchored in a substantially fixed position within the primary anatomical conduit (e.g., aorta A). In applications wherein the endoluminal grafting system 10 is being used to repair an aneurysm, the hemodynamic pressure within the aneurysm sac (i.e., the space within the aneurysm but outside the primary graft 12), as well as the hemodynamic pressure within the branch anatomical conduit(s) which emanate from the aneurysm, will be substantially unaffected by the initial placement of the primary graft 12 because, until such time as the branch graft(s) 14 have been introduced, blood will continue to flow out of the branch graft opening(s) 14 of the primary graft 12.
After the primary graft 12 has been positioned and anchored within the primary anatomical conduit (e.g., aorta A), a guidewire 30 may be transluminally advanced through the lumen of the primary graft 12, out of a branch opening 14 and into the branch anatomical conduit (e.g., In some applications, a guide catheter may be introduced into the lumen of the primary graft 12 to facilitate passage of the guidewire 30 out of the desired branch graft opening 14.
A branch graft 16 is then mounted on a balloon catheter 32, and the distal end of the branch graft may be drawn taught about the catheter balloon 34 by a purse string suture 36 (e.g., 7.0 polypropylene suture material). The balloon catheter 32 having the branch graft 16 mounted thereon is then advanced over the guidewire 30 until the proximal end of the branch graft 16 becomes connected to the branch graft opening 14 of the primary graft 12 by way of the branch graft connector apparatus 17. Thereafter, the catheter balloon 34 is inflated, causing the purse string suture 36 to break and the distal end of the branch graft 16 to radially expand into contact with the surrounding wall of the branch anatomical conduit.
A branch graft connector apparatus 17 is shown in detail in FIGS. 1B-1D. The components of this branch graft connector apparatus 17 associated with the primary graft 12 comprise: a first rigid or semirigid ring 40 which surrounds the branch graft opening 14, and a rigid or semirigid frustoconical member 42 which extends outwardly from the first ring member 40, as shown in FIG. 1B. The components of this branch graft connector apparatus associated with the branch graft 16 comprise a rigid or semirigid, tapered proximal portion 44, a second rigid or semirigid ring member 46 on the proximal end of the tapered proximal portion 44, and a third rigid or semirigid ring member 48 formed about the tapered proximal portion 44 at a spaced distance from the second ring member. The distance between the outer surface OS of the second ring member 46 and the inner surface IS of the third ring member 48 is substantially the same as the distance between the inner surface IS of the first ring member 40 and the distal end DE of the frustoconical member 42. In this manner, as the branch graft 12 is advanced, distal end first, out of the branch graft opening 14 it will reach a point of maximum advancement where at the inner surface IS of the first ring member 40 will abut against the outer surface OS of the second ring member 46, and the distal end DE of the frustoconical member 42 will abut against the inner surface IS of the third ring member 48. This will create a substantially fluid-tight seal between the proximal end of the branch graft 16 and the body of the primary graft 12. Additionally, this may form a snap-fit connection which will prevent the branch graft 14 from slipping or undergoing inadvertent retraction back into the lumen of the primary graft 12.
It will be appreciated that an audible or tactilely discernible indicator (e.g., a “snap”) may occur as the separate components of the branch graft connector 17 come together, thereby indicating to the operator that the desired engagement and sealing of the proximal end of the branch graft 16 to the primary graft 12 has been accomplished.
Thus, a need exists for a method and deployment system that enables partial deployment of a stent-graft while constraining a proximal end of the stent-graft, provides adequate control to enable re-deployment of the stent-graft in various dimensions and further reduces deployment forces during advancement of the stent-graft to enable aligned deployment of branch grafts with corresponding branch vessel openings. Ideally, such a branch graft is a part of a system of grafts that can treat no-neck and thoraco-abdominal aortic aneurysms using a branch that makes a fluid tight connection to a port of the main graft.
In addition, there remains a need in the art for the development of new endovascular grafting systems and methods which a) may be useable for endovascular grafting in regions of a blood vessel (e.g., aorta) from which branch blood vessels (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, renal or iliac arteries) extend, and/or b) may enable more aortic aneurysm patients to be considered as candidates for endovascular repair, and/or c) may otherwise advance the state of the art of endovascular grafting to improve patient outcomes or lessen complications.